Git support

You can track files generated by scala-bootstrapper in a Git branch, and
later merge changes from the branch (e.g. to rename a project, or to
upgrade to a newer version of scala-bootstrapper.

To get started:

:$ scala-bootstrapper --git foo

For a brand-new project (no .git directory) this will initialize a
Git repo in the directory, generate files into the
scala-bootstrapper branch, and merge the branch to
master.

For an existing project, this will generate files into the
scala-bootstrapper branch, and merge it to the current branch
without actually taking the changes (just making
scala-bootstrapper a parent of the current branch to anchor future
merges). This is to avoid clobbering files if you had previously run
scala-bootstrapper without the --git option (or created
files some other way). If you want to merge the changes and manually
resolve any conflicts, do

:$ git cherry-pick --no-commit scala-bootstrapper

Once the scala-bootstrapper branch is created, subsequent runs
will generate files into the branch and merge it to the current branch; if
there are conflicts you can resolve them in the usual way.